Treatment of hydrocarbons



WEIGHT PERCENT H F WEIGHT PERCENT H2O Jan. 3, 1950 D. E. BERGEN TREATMENT OF HYDROGARBONS Filed May 27, 1946 2 Sheets-Sheet l 3 4 RESIDENCE TIME. HOURS RESIDENCE TIME, HOURS INVENTOR. D. E. BERGEN BY 7fMm $M AT TOR Jan. 3, 1950 D. E. BERGEN TREATMENT OF HYDROCARBONS Filed May 27, 1946 2 Sheets-Sheet 2 mjurumm Patented Jan. 3, 1950 2,493,384 TREATMENT OF monocsnnons Daniel E. Bergen, Phillips, Tex., assignor to Phillips Petroleum Company, a corporation of Delaware Application May 27, 1946, Serial No. 672,475

1 Claim.

This invention relates to the conversion of hydrocarbons. In one aspect this invention relates to the purification of acid-soluble oils. In another aspect this invention relates to the alkylation of hydrocarbons in the presence of a hydrofluoric acid alkylation catalyst. In another and more particular aspect this invention relates to the production of a drying oil.

In the conversion of hydrocarbons in the presence of inorganic acid catalysts, such as hydrofluoric acid or sulfuric acid, acid-soluble oils are formed as by-products of the conversion reaction and contaminate the acid phase of the conversion process. For example, in the alkylation of an alkylatable hydrocarbon with an olefin in the presence of a hydrofluoric acid alkylation catalyst, acid-soluble oils accumulate in the acid phase to such an extent as to decrease the activity of the catalyst and yield of product. The contamination of the acid phase of such an alkylation process with acid-soluble oils necessitates the removal of acid-soluble oils from the acid. As the acid is also contaminated with water which is detrimental to the acid activity the acid-soluble oils are usually removed during the purification of the acid to remove the water therefrom. The separated oil phase contains from about 0.5 to about 15 weight per cent hydrogen fluoride and in many cases a small amount of water. Since this acid-soluble oil as separated has had little value, it has been disposed of as a waste product. However, its disposal constitutes a dangerous health hazard since the acid in the oil cannot be neutralized because of the presence of the oil. From the viewpoint of the disposal of the acidsoluble oils and for their possible usefulness, it is much to be desired to provide amethod to re-' move the acid from the acid-soluble oils.

The object of this process is to provide a method for the separation and recovery of acid-soluble oils from the effluent of a hydrocarbon conversion process.

It is another object to decrease the difficulty of disposal of acid-soluble oils.

It is another object to purify acid-soluble oils obtained from a hydrocarbon conversion process using an inorganic acid catalyst.

' A further object of this invention is to provide a process for the production of acid-soluble oils of high quality and high purity.

Still another object is to manufacture a drying oil of superior characteristics to other known drying oils.

A further object is to decrease the difficulty of disposal of oil wastes from a hydrocarbon convermoval of acid-soluble oils from a hydrocarbon conversion efiluent and the purification of these acid-soluble oils so that they may be recovered as a useful and valuable product or disposed of without difficulty. Accordingly in a process for the conversion of hydrocarbons in the presence of a hydrofluoric acid catalyst in which the hydrocarbon conversion efiluent is separated into a liquid hydrocarbon-rich phase and a heavier liquid hydrofluoric acid-rich phase and the hydrofiuoric acid-rich phase is treated to remove water and acid-soluble oils therefrom, such as by a series of distillations, the acid-solubleoils which are recovered'during the treatment of the hydrofluoric acid catalyst and which are contaminated with water within the range between about 5 and about 15 weight'per cent and with hydrofluoric acid within the range between about 0.5 and about 10 weight per cent are subsequently treated to remove hydrogen fluoride therefrom. This treatment to remove hydrogen fluoride from the acid-soluble oils comprises admixing approximately equal volumes of water and acid-soluble oil and allowing the resulting mixture of water and acid-soluble oil to settle at a temperature between about and about 210 F. for sufiicient length of time for a phase separation to occur and to allow the water phase to extract hydrogen fluoride from the hydrocarbon phase. It is extremely important that sufficient time be allowed for the water phase to extract hydrogen fluoride from the-hydrocarbon phase at the'appropriate temperatureysuch time being at least about one hour and preferably between about 3 and about 5'hours. The ratio of water to acid-soluble oils in the abovetreatment is also important and should be at least about a 1:1 volume ratio and may be as high as about a 3:1 volume ratio. In mostinstances'the "oil itself is not heated but water at a temperature between 200 and 210 F. is admixed therewith which raises the temperature of the resulting mixture sufliciently high to achieve adequate extraction of the hydrogen fluoride from the acid-soluble oils. The process may be carried out in either a batch operated process or a continuous operated process without departing from the scope of this invention and with equal successful extraction of acid from the acid-soluble oil fraction.

In a batchwise process, the washing treatment of the acid-soluble oils may be repeated as many times asdesired and as'isn-ecessary'to remove a sufiicient amount of the hydrogen fluoride from the acid-"soluble oil fraction. Figures 1 and 2 of the drawings show graphically the composition of the hydrocarbon phase after treatment according to this invention and after settling for a period of-time indicated on the abscissa of the graphs. The ordinate of the graph of Figure 1 indicates the composition of the hydrocarbon phase with respect to hydrogen fluoride content. The ordinate of the graph of Figure 2 indicates the composition of the hydrocarbon phase .with respect to the water content. It is clear from Figures 1 and 2 that to obtain maximum efficiency of the washing step at least one hour residence time should be allowed for either a ,batchwise or continuous process. The curves of-Figures l and 2 were derived from data shown -in Table II of Example II of this specification.

Typical acid-soluble oil fractions which may be treated according to the process described .herein vary considerably in compositiombut are, in general, normally liquid and are soluble dn-hydros gen fluoride and partially soluble in water and in hydrocarbons. The acid-soluble oil fractions vary in A. -P. I. gravity between about 15 and about 30 degrees and possess an iodine number (a measurementof unsaturation) between about 175 and about 250. Generally, the 10-90 volume per cent boiling range determined-by vacuum distillation and corrected to a pressure of '760 mm., is within the range-betweenabout 300 and about 1000 F. About 60 to 85 weight per cent of the acid-soluble oil fractions comprise non-volatile material at atmospheric pressure. Acid and water remaining in the acid-soluble oil fractions after treatment of the fractions are less than about 0.05 weight per cent and about 2 weight per cent, respectively.

The inventionmayperhaps be more adequately understood by reference to Figure -3 of the accompanying drawings and the .description thereof. Figure 3 represents diagrammatically the preferred arrangement of apparatus elements and flow of materials thereto-in which .theprocess of the present invention may-be practiced. While the elements essential to the .understandingof the invention are shown in Figure 3, it will be appreciated that various auxiliary pieces of equipment may be provided by oneskilled in the art without departing from the scope of this invention. Since the valkylation of an alkylatable hydrocarbon in the presence of a hydrofluoric acid catalyst produces a considerableamount of acid-soluble oils in the liquid acid phase, usually between about -5 and about '20 percent, this invention as applied to such an alkylation process willbedescribed.

In the alkylation of isobutane with oleflns in the presence of hydrofluoric acid as the alkylation catalyst-a suitable and typical feedstock of the hydrofluoric acid alkylation in which the acid-soluble oils are a -by-product.appears in Table.I below:

Table. I

Component "Mel per cent Isobutane '68 Isobutylene 4 Normal butylene. 7 Butane 20 Other hydrocarbons 1 pounds per square inch gage. :sired, however, both higher pressures and higher temperatures may be used. In general, only sufficient pressure to ensure liquid phase operation is necessary. From reaction zone 5 a hydrocarbonlconversion effluent is passed by line 8 to separation zone 9 in which the effluent separates into two liquid phasesnamely, a lighter hydrocarbon-rich phase and a heavier hydrogen fluoride-rich phase. The hydrogen fluoride-rich phase is withdrawn from thebottom of separator 9 through line [9 to be recycled as a catalyst for the alkylation reaction through lines I9 and '1. Fresh make-up hydrofluoric acid may be added to the system through line I when desired. When it is desirable to remove water and to recover acid-soluble oils from the acid-phase in order to ensure the proper function of the catalyst or to recover the acid-soluble oils as a valuable byproduct, a portion or all of the hydrogen fluoride phase is .pased through line 2| to apurification .unit 22, the operation of which will be discussed hereinafter. An azeotropic mixture of water and hydrogen fluoride and acid-soluble oils are separately removed from purification unit 22 through lines 24 and 25, respectively. A purified anhydrous acid phase is passed from purification unit 22 through lines 23, i9 and I to reactor '6.

A liquid hydrocarbon-rich phase containing dissolved hydrogen fluoride passes from separator .9 through line H to separating unit [2. In separating unit [2, which may .comprise a single or .a series of :distillation zones, approximately an .azeotropic mixture of hydrogen fluoride and low-boiling hydrocarbons, such as isobutane, is separated and is passed therefrom through line .l3 back to separator .5. Isobutane is separated from the reaction efliuent in separating unit l2 andrecycled toreactor 6 through line I4. 'Normal butane and other intermediary products are withdrawn from separating unit l2 through line I 6. The normal butane may be isomerized to isobutane and .used as a portion of the feed. The alkylation product comprising a light alkylate andheavy alkylateis withdrawn from separating unit 12 vialine l1 and may be passed to further equipment .(not shown) for purification and separation.

Referring to purification unit 22, several methods are known to those skilled in theart for removing water and acid-soluble oils from the acid phase. :A typical and generally used method comprises passing the acid phase to a series of distillation columns. The first column comprises, in general, a flash-distillation column in which hydrogen fluoride and water pass overhead as a vapor and the acid-soluble oils containing some free hydrogen fluoride is removed as a bottom product. The hydrogen fluoride and water overhead after condensation is passed to asecond distillation column, from which substantially anhydrous hydrogen fluoride is removed as an overhead fraction and aliquidazeotropic mixture of water and hydrogen fluoride is removed as a .bottom fraction. In some instances a single distillation column may be used to purify the acid phase. An acid-water azeotrope containing the acidsc bl oil is m frem the bo om o the distillation column. The liquid bottom fraction isv allowed to. settle for suflicient length of time to form a hydrocarbon phase and a wateracid phase. The hydrocarbon phase comprises the acid-soluble oils. In either of these'meth, ods for recovering acid-soluble oils from the acid phase, the acid-soluble oil fraction recovered contains between about 5 and about weight per cent water and between about 0.5 and about 10 weight per cent hydrogen fluoride. The acid! soluble oils constitute about 10 weight per cent of the original acid phase. Often economic and operational considerations dictate the omission of the. aforementioned step for the separation of the acid-soluble oil from the resulting acidwater azeotrope in purification unit 22. When this optional separation step is omitted, a mixture of water, acid and acid-soluble oil is passed directly through line 26 tc the washing step hereinafter described and line 24 is not used.

' In order to purify such an acid-soluble oil fraction according to this invention, the acid-soluble oil fraction isspassed from acid purification unit 22 hrough line 26 to mixing or prewash tank 21. The acid-soluble oils from line 26 are extruded through a perforated ring (not shown) into a hot layer of water (between about 200 and about 210 F.) in tank 27. The acid-soluble oils and water in tank 2! may be agitated by mechanical means if desired. Approximately 90 per cent of the hydrogen fluoride in the acid-soluble oil fraction is removed in tank 21 and is removed therefrom as an aqueous solution through line 29. Hot water at a temperature between about 200 and about 210 F. is passed into tank- '21 through line 33. The washed acid-soluble oil fraction rises to the top of the water layer in tank 21 and overflows therefrom through line 28 and is passed to a settling tank 3|. Hot water at a temperature between about 200 and about 210 F. is introduced into line 28 through line 32 and is admixed therein with the washed acid-soluble oil fraction from tank 21 in about 2:1 volume ratio. A mixing pump or orifice device (not shown) may be inserted on line 28 to thoroughly mix the water and the acid-soluble oil fraction prior to introduction into settling tank 3|. In settling tank 3i a liquid hydrocarbon phase comprising purified acid-soluble oils and a liquid water phase is separated by settling for several hours. The water phase contains hydrofluoric acid extracted from acid-soluble oil fraction and is removed therefrom through line 31. This water-acid phase may be withdrawn from the system through line 37 or may be passed through lines 38, 32 and 33 to prewash tank 21, if desired. The purified acid-soluble oil fraction forms an upper layer in tank 3| and is withdrawn therefrom through line 36. Impurities in the acidsoluble oil fraction withdrawn through line 36 range between about 0.03 and about 0.01 per cent by weight of acid and between about 0.6 to about 0.4 per cent by weight of water.

A temperature between about 175 and 210 F., preferably above 200 F., and a residence time between about 1 to about 5 hours of the liquid mixture is maintained in tank 3|.

The acid-soluble fraction purified according to this invention is of very high purity and is useful as a drying oil. Comparative tests indicate that the purified acid-soluble oils have a higher viscosity, a higher per cent nonvolatility, a higher iodine number and a lower polymer color than ether similar drying oils. Also the purified acidsoluble oil fraction appears/to form a tougher, harder film when exposed to the air than other drying oils. When it is not desired to recover the acid soluble oil fraction as a product, the disposal problem is minimized by such a treatment since no hydrogen fluoride is contained in the oils but remains in the water phase, which may be neutralized with an alkali in the conventional manner.

The following examples are offered as illustrative ofthe'operation and product of the present invention and should not be construed to unnecessarily limit this invention.

EXAMPLE I An acid-soluble oil fraction from an alkylation process acid regeneration unit, such as unit 22 of Figure 3, containing approximately 7 weight per cent hydrogen fluoride was charged to a prewash tank, such as tank 2:1. After the acid-soluble oil fraction has passed through an approximately equal volume of water at about 200 in this prewash tank, it contained about 0.2 weight per cent hydrogen fluoride. The prewashed oil was removed from the prewash tank and mixed with an equal volume of hot water at approximately 210 F; in a mixing pump and then passed to a cooling tank and allowed to stand at-about 200 F. After about minutes the acid-soluble fraction contained about 0.008 weight per. cent hydrogen fluoride, and after nearly two hours contained only about 00.01 Weight per cent hydrogen fluoride. The wash water containing the acid wasoil free and could be easily neutralized without the interference encountered when oil was present.

EXAMPLE II Five gallons of an acid-soluble oil fraction from an acid purification unit of an isobutane alkylation process was charged to a tank equipped with steam coils. The oil was heated to a temperature of approximately 210 F. During the same period, water in a secondary tank was heated to its boiling point. The hot oil and water were fed through a pump in about a 1:1 ratio and charged back to the secondary tank for settling. After the oil in the charge tank had all been pumped, the mixture was allowed to settle 30 minutes. The water was drained and the oil transferred to the first tank, after which the procedure was repeated with fresh water.

Following the second wash the separating mixture was kept hot by an exterior coil to facilitate phase separation. Samples of the oil were taken after A, /2, 1, 2, etc. hours and the hydrogen fluoride and water content determined. The composition of the hydrocarbon phase with respect to water and hydrogen fluoride for the various residence times is indicated in Table II below. The data of Table II is shown graphically in Figure 1 and 2 of the drawing.

Table II Per cent by Per cent b Residence Tune Weight, H1O weight, H%

EXAMPLE III Characteristics of acid-soluble oil fractions purified according to the treatment of this invention are shown in Table III below:

Table III,

Saybolt For sample Flash Fire Universal A.P.I. 11 Cent 2 Point Point Viscosity Gravity No. Non- Color at 210 F. vol.

Various apparatus elements, such as valves,

cooler, heater, mixers, etc. have been omitted from the drawing for the matter of convenience. Consequently various alterations and modifications may become apparent to those skilled in the art without departing from the scope of this invention.

I claim:

In a process for the alkylation of hydrocarbons in the presence of a hydrofluoric acid catalyst in which an effluent from said alkylation is separated into a hydrocarbon-rich phase and a liquid hydrofluoric acid-rich phase and the acid-rich phase is treated to separately recover therefrom said acid catalyst and an acid-soluble oil fraction containing residual acid, the method for treating said acid-soluble oil fraction to prepare an acid-soluble oil product and an innocuous aqueous suspension by-product, which comprises admixing therewith at least an equal vol- 8 ume of hot liquid water at a temperature of about 200 F. to 210 F., allowing the resulting liquid mixture of water and acid-soluble oil to settle for a period of at least one hour at a temperature between about and about 210 F. under conditions such that a liquid hydrocarbon phase and a liquid water phase separate, thereby extracting said residual acid from the acid-soluble oil fraction, recovering said hydrocarbon phase substantially free from acid as a purified acid-soluble oil product of said extraction, separately recovering said liquid water phase substantially free of oil and containing said residual acid and neutralizing said liquid water phase with an alkali to form an innocuous suspension of a fluoride salt before disposal thereof as said byproduct of the process.

DANIEL E. BERGEN.

REFERENCES CITED The following references are of record in the file of this patent:

- -UNITED STATES PATENTS Number Name Date 1,872,463 Jones Aug. 16, 1932 2,141,297 Harrington Dec. 27, 1938 2,301,335 Showalter et al. Nov. 10, 1942 2,342,677 Linn Feb. 29, 1944 2,343,791 ODell Mar. 7, 1944 2,354,554 Showalter et al. July 25, 1944 2,392,048 Kassel Jan. 1, 1946 2,404,393 Mayland July 23, 1946 2,413,310 Bloch Dec. 31, 1946 2,425,584 Wadley et al. Aug. 12, 1947 

